Telephone-exchange system.



H. w. MACDOUGALL.

TELEPHONE EXCHANGE SYSTEM.

APP'LICATloN FILED ML2, 191s.

Patented Sapt 3,19%,

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STATES, PATENT WEEE.

HARRY W. MAoDOUG-ALL, OF EAST ORANGE, NEW JERSEY, ASSIGNOR 'IO WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

Lawaaa.

Application filed January 2, 1918.

To all whom t may concern:

Be it known that I, HARRY lV. MAC- DoUGALL, a citizen of the Unit-ed States, residing at East Orange, in the county of Essex, State of New Jersey, have invented certain new and useful Improvements in Telephone-Exchange Systems, ot' which the following is a full, clear, concise, and eXact description.

This invention relates to telephone eX- clrange systems and more particularly to such systems employing trunk circuits extending between tWo central otlices over which connections may be established between telephone lines terminating at the different otlices. y

An object oi this invention is the provisionof improved signaling means for systems ot this character.

In accordance with this invention, a trunk circuit extending from central oliice of the central energy type to a central oliice of the magneto or local battery type, is provided With apparatus for automatically connecting a source of ringing current to the trunk circuit upon'connection therewith at the central energy ollice ot' a link circuit to cause the operation of a signaling device at theV magneto otlice, which current is then automatically disconnected from the trunk circuit. when connection is made therewith at the magneto olice. i

One embodiment of this invention is illustrated Vin the accompanying drawing in which a trunk circuit A extends from a ,central oilice X of the central energy type to a central olilce Y of the magneto type.` A

cord circuit C provided at the central oliice X may be connected With the trunk circuit A, while a cord circuit D provided at the magneto otlice may be connected with the other end of the link circuit. All apparatus shown in the left of the dotted line 2, 2 et the drawing is located at the central otlice X and that shown to the right thereof is located at the magneto office Y. At the central oliice X the link circuit terminates in a jack 5 located at a local subscribers position and in a jack 6 located at a toll position.

Specification of Letters Patent.

Patented Sept. 3, 1918.

seriaino. 209,969.

Assuming that the operator located at the s ubscribers position of central oflice X desires tol signal the operator at the magneto oliice Y, calling plug 7 of the cord circuit C is inserted into the jack 5 of the trunk circuit. Calling supewisory lamp 8 is thereby lighted and relay 9 operated over a circuit from battery through the lamp 8 the Winding of relay 9, sleeve contacts of the plug 7 and the jack 5, middle normal contacts of relay 10, contact of relay 18, and normal contacts of relay 11 to ground.

Relay 9 in operating causes the operation of ringing relay 12 over a circuit from battery through resistance 13, the Winding of relay 12, the normal contact of relay l-l, the Contact of trip relay 15, and the Contact of relay 9 to ground. Ringing relay l2 1n operating connects ringing currentV to the trunk over a circuit from a source or' ringing current 16 through the Winding of trip relay 15, lower alternate contact of ringing relay 12, ring contacts of the plug 7 and the `iack 5, upper normal contact of relay 17, the Winding of relay 18, tip contacts of the jack 5 and the plug 7, and the Vupper alternate Contact of ringing relay 12 to ground. Trip relay 15 and relay 18 are immediat-ely operated over this circuit. The operation of the trip relay 15 opens a short circuit about the Winding of relay 14 which is thereupon energized to complete a short circuit about the Winding of ringing relay 12.` Ringing relay 12 thereupon releases, disconnecting ringing current fromV the trunk. Relay 14 in operating also completes a locking circuit for itself from battery through the resistance 13, alternate contact and Windingof relay 1-1, and the Contact of relay 9 to ground. Relay 18 in opera-ting opens its contact, removing` a short circuit Jfrom the Winding of relay 11 which is thereupon operated, opening its normal and closing its alternate contacts.

Relay 11 in operating also causes the operation of relay 17. Relay 17 thereupon opens its normal and closes its alternate contacts, the closure of its upper alternate contact closes a normal break in the ring strand of the trunk circuit and the opening of its upper normal contact disconnects relay 18 from across the talking conductors of the trunk circuit. The closure of the lower alternate contact 25 of relay 17, causes the operation of relay 26 over a circuit from battery through the right-hand winding of retardation coil 27, contact 28 of jack 29, upper normal contact of relay 10, winding 43 of repeating coil 38, contact 25 of relay 17 windings of relay 26, winding 44 of repeating coil 38, lower normal contact of relay 10, contact 30 of jack 29, and lefthand winding of retardation coil 27 to ground. Relay 26 in operating opens its normal and closes its alternate contacts, thereby causing the operation of relays 31 and 32 over a circuit from battery through alternate contact 35 of relay 17, alternate contact of relay 26, left-hand contact of relay 36, and the winding of relay 31 and the upper winding of relay 32 in parallel to ground. Relay 31 in operating connects a source of ringing current 37 in circuit with the two windings 40 and 41 of the repeating coil 38. This circuit may be traced from a source of ringing current through the alternate contact 39 of relay 31, the winding 40 of the repeating coil 38, contact of relay 32, the winding 41 of the repeating coil 38, and contact 42 of relay 31 to ground. Current is thereupon induced into windings 43 and 44 of the repeating coil which are in circuit with the winding of a drop 45. The coil of this drop is thereupon energized, attracting its armature and dropping its shutter which furnishes a signal to the operator at the magneto oilice. `Relay 31 in operating as before described opens up the talking circuit of the trunk, completes a locking circuit for itself through its contact 46, and in addition causes the operation of relay 36 over a circuit from battery through contact 35 of relay 17 right-hand winding of relay 3'6 and Contact 48 of relay 31, to ground. Relay 36 in operating opens its left-hand contact which is in the initial energizing circuit of relays 31 and 32, and closes its right-hand Contact, thereby establishing a locking circuit for itself. Ringing current from source 37 remains connected with the trunk circuit until the operator at the magneto oflice answers.

The operator at the magneto ,oiiice Y observing that the shutter of the drop 45 has fallen, inserts plug 50 of the cord circuit D into the jack 29, thereby opening contacts 30 and 28 and disconnecting from the trunk circuit battery supplied through the windings of the retardation coil 27. Relay 26 thereupon releases its armature, opening a contact in the circuit which includes the winding of relay 31vand the upper winding of relay 32. These relays thereupon release their armatures. Relay 31 in releasing disconnects ringing current from the trunk circuit and closes the talking circuit thereof. Relay 32, however, is immediately operated again upon the closure of the normal contact of relay 26. The circuit therefor may bc traced from battery through contact 35 of relay 17, normal contact of relay 26, and the lower winding of relay 32 to ground. Since relay 31 is now denergized when relay 32 closes its contact, supervisory relay 55 of the cord circuit C operates over a circuit from battery through the winding of supervisory relay 55, lower normal contact of ringing relay 12, ring contacts of the plug 7 and the jack 5, upper alternate-contact of the relay 17, lower normal contact of relay 31, winding 4() vof the repeating coil 38, contact of relay 32, winding 41 of repeating coil 38, upper normal contact of relay 31, tip contacts of the jack 5 and the plug 7, and upper normal contact of ringing relay 12 to ground. Supervisory relay 55 in operating completes a shunt including resistance coil 13 for the calling supervisory lamp 8, thereby extinguishing the lamp. The extinguishment of this lamp indicates to the originating operator that themoperator at the magneto oliice has answered.

lVhen the operator at the magneto ofhce withdraws the plug 50 from the jack 29, the circuit of relay 26 is established, energizing the relay. The opening of the normal contact of relay 26 causes the denergization of relay which opens its contact.V Supervisory relay 55 is thereby denergized and the supervisory lamp 8 is lighted to furnish a disconnect signal tothe originating operator. The closure of the alternate contact of relay 26 does not cause the renergization of relays 31 and 32, for the left-handV contact of relay 36 which is in the initial energizing circuit of relays 31 and 32 is now open, relay 36 being locked up.` In this way ringing current cannot be connected with the trunk circuit upon the disconnection of the cord circuit D therefrom. The operator at the central oflice X, upon observing the disconnect signal 8, withdraws the plug from the jack 5, lwhereupon all apparatus is restored to its normal condi-v tion.

rlhe operator at the magneto ofce Y may signal the operator at the local position or the operator at the toll position of the central o'llice X. To do so the plug 50 of the cord circuit D is first inserted into the jack 29 of the trunk circuit A. Wishing to signal the operator atthe local position, ringing key 6() is actuated, thereby causing the operation of relays 61 and 36 over a circuit from a source of ringing current 62 through the contact of ringing key 60, ring contacts of the plug 50 and the jack 29, lower normal contact of relay 10, winding 44 of repeating coil 38, condenser 63, left-hand winding of relay 61, left-hand winding of relay 36, and middle normal contact of relay 17 to ground.

Relay 61 in operating lights the lamp 64 which is associated with the jack 5, and establishes a locking circuit for itself through its right-hand winding, the lamp 64 being lighted and the locking circuit being maintained over a circuit including the left-hand Contact of relay 61 and the middle normal contact of relay 17. Relay 36 in operating, closes its right-hand contact, establishing a locking circuit for itself from battery through the right-hand contact of relay 61, right-hand winding and right-hand contact of relay 36 to ground. One reason for operating and locking up relay 36 when relay 61 operates is to open the normal contact of relay 36 so that when the operator inserts plug 7 into jack 5, relay 31 cannot be energized. In this way ringing current cannot be connected with the trunk.

Upon the insertion of the plug 7 into the jack 5, relays 9, 12,14 and 15 of the cord circuit and relays 18, 11 and 17 of the trunk circuit operate in the manner hereinbefore described. Upon the operation of relay 17, relay 32 is operated over a circuit from battery through the contact 35 of relay 17, normal contact of relay 26, and the lower winding of relay 32 to ground. Relay 32 thereupon closes its contact, establishing an energizing circuit for the supervisory relay 55 which attracts its armature to extinguish the supervisory lamp 8. Relay 17 in operating also opens the locking circuit of relay 61 which releases and extinguishes thelamp 64. Relay 36, however, remains locked up until the release of' relay 17' upon the subsequent removal of the plug 7 from the jack 5, for battery to the right hand winding of'relay 36 is furnished through contact 35 of relay 17.

Should the operator at the mag'neto oiiice Y desire to signal the toll operator, ringing key instead of 60 is actuated to connect a source of ringing current 71 with the trunk circuit, thereby causing the operation of relays 72 and 36 over a circuitfrom the source of ringing current 71, through the contact of ringing key 70, `tip contacts of theplug 50 and the jack 29, upper normal contact oi' relay 10, winding 43 of the repeating coil 38, condenser 73, right-hand winding of relay 72, left-hand winding of relay 36, and the middle normal contact of relay 17 to ground. Relay 7 2 in operating establishes a lockimg` circuit for itselfl from battery through the lower normal contact of relay 17. left-hand contact and left-hand winding of'relay 72 to ground. rIfhe lamp 74 associated with the jack 6 isin parallel with the left-hand winding of relay7 2 and is lighted when this locking circuit is completed. The

closure of the right-hand Contact of relay 72 completes a locking circuit through the right-hand winding of relay 36. The toll operator upon observing the lighted condition of the lamp 74 inserts into the jack 6 the plug of a cord circuit, the sleeve strand of which is connected with battery, thereby causing the operation of relay 10.

Relay 10 `in operating causes the energization of relay 11 over a circuit 'from battery through the alternate contact of relay 10, and winding of relay 11 to ground. Relay 11 thereupon causes the operation of relay 17 to extinguish the lamp` 74 and release the relays l72. Relay 36 remains locked up until thetoll operator disconnects the plug from the jack 6. Relay 10 in Operating also opens up contacts in the talking conductors of the trunk circuit, thereby disconnecting the local position end of the trunk to prevent any interference from a local operator. It will also be observed that the closure of the alternate contact of relay 10 connects a busy test potential to the local jack.

What is claimed is:

1. A telephone exchange system comprising a trunk circuit extending from a first to a second switchboard, a source of' ringing current, a link circuitat the iirst switchboard, means in the trunk circuit responsive to the connection of the link circuitwith the trunk 4circuit to connect therewith the source of ringing current, a signaling device at the second switchboard operated by current from said source, a switching device at the second switchboard, and means responsive to the actuation of the switching device for disconnecting the source of ringing current from the trunk circuit.

2. A telephone exchange system comprising a trunk circuit extending from a first to a second switchboard, `a source of ringing current, a link circuit at the first switchboard, a relay in the trunk circuit operating when the link circuit isconnected therewith to connect the source of ringing current with the trunk circuit, a signaling device at the second switchboard operated by current from said source, switching mechanism at the second switchboard, and means responsive to theoperation of the switching mechanism for disconnecting the source of ringing current from the trunk circuit.

3. A telephone exchange system comprising a trunk circuit extending 4from a first to a second switchboard, a source of ringing current, a link circuit at the first switchboard, an electromagnetic switching device in the trunk circuit actuated when the link circuit is connected therewith to connect the source of ringing current with the trunk circuit, a signaling device .at the second switchboard operated by current fromsaid source, a link circuit at the second switchboard, and means responsive to the connection thereof with the trunk circuit for disconnecting the source of ringing current therefrom.

4. A telephone exchange system comprising a trunk circuit extending from a irst to a second switchboard, a source of ringing current, a link circuit at the iirst switchboard, an electromagnetic switching device in the trunk circuit actuated when the link circuit is connected therewith to connect the source of ringing current with the trunk circuit, a signaling device at the second switchboard connected with the trunk circuit and operated by current from said source, a link circuit at the second switchboard, and means responsive to the connection thereof with the trunk circuit for dis-y Y. rent 'from said source, a link circuit at the second switchboard, and switching mechanism actuated upon the connection of the link circuit with the trunk circuit for disconnecting the signaling Vdevice and the source of ringing current therefrom.

G. A telephone exchange system comprising 'a trunkl circuit extending from a first to a second switchboard, a source of ringing current and a link circuit at the irst switchboard, switching means responsive to the connection of the link circuit with the trunk circuit, a source of direct current and a signaling device at the second switchboard, and an electromagnetic switching device actuated by current from the direct current source upon the response of the switching means to connect the source of ringing current with the trunk circuit for operating the signaling device.

7. A telephone exchange system comprising a trunk circuit extending i'rom a iirst to a second switchboard, a source of ringing current and a link circuit at the first switchboard, a relay responsive to the connection oi. the link circuit with the trunk circuit, a source of direct current and a signaling device at the second switchboard, and electromagnetic means actuatedloy current from the direct current source upon the response of the relay for connecting the source of ringing current with the trunk circuit for operating the signaling device.

8. A telephone exchange system comprising a trunk circuit extending from a first the source of ringing current with the trunk circuit for operating the signaling device.

9. A telephone exchange system comprising a trunk circuit extending from a lirst to a second switchboard, a source of ringing current and a link circuit at the iirst switchboard, a relay in the trunk circuit energized upon connection oi. the link circuit therewith, a source of direct current and a signaling device at the second switchboard, a second relay responsive to current from the direct current source when the first relay is energized, a third relay actuated upon the response of the second relay when the first relay is energized to connect the source of ringing Vcurrent with the trunk circuit for operating the signaling device, an operatorcontrolled switching device at the second switchboard, and means in the trunk circuit responsive to the actuation of the switching device for disconnecting the source of ringing current from the trunk circuit.

10. A telephone exchange system comprising a trunk circuit extending from a iirst to a second switchboard, a source oi ringing current in the link circuit at the iirst switchboard, a relay in the trunk circuit energized upon connection of the link circuit therewith, a source of direct current at the second switchboard, a signaling device thereat connected with the trunk circuit, a second relay responsive to current from the direct current source when the irst relay is energized, a third relay actuated upon the response of the second relay when the first is energized to connect the source of ringing current with the trunk circuit for operating the signaling device, a link circuit at the second switchboard, and means responsive to the connection of the link circuit with the trunk circuit for disconnecting the signaling device and the sourceof ringing current therefrom.

11. A telephone exchange system comprising a trunk circuit extending from the rst to a second switchboard, a source of ringing current and-a link circuit at the irst switchboard, a relay in the trunk circuit energized upon connection of the link circuit therewith, a source of direct current and a signaling device at the second switchboard, a second relay responsive to current from the direct current source when the iirst relay is energized, a third :relay energizedupon the response of the second relay while the first relay is energized to connect the source of ringing current with the telephone circuit for operating the signaling device, a locking circuit for the third relay established upon the energization thereof, a fourth relay responsive to the energization of the third relay to open the initial energizing circuit of the third relay, a link circuit at the second switchboard, and nieans responsive to the connection thereof with the trunk 10 circuit for causing the opening of the locking circuit of the third relay, thereby to disconnect the source of ringing current from the trunk circuit.

In Witness whereof, I hereunto subscribe 15 my name this 28th day of December A. D., 1917.

HARR W. MAODOUGALL.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents, Washington, D. C. 

